Gasoline fuel composition



United States Patent 3,481,718 GASOLINE FUEL COMPOSITION Walter F. Schoen, South Holland, and Fred L. Voelz, Or-

land Park, Ill., assignors to Sinclair Research, Inc. New York, N.Y., a corporation of Delaware No Drawing. Continuation of application Ser. No. 418,855, Dec. 16, 1964. This application Jan. 15, 1969, Ser. No. 796,277

Int. Cl. Cl 1/30 US. Cl. 44-69 10 Claims ABSTRACT OF THE DISCLOSURE A gasoline composition consisting essentially of hydrocarbon gasoline, an anti-knock quantity of tetraloweralkyl lead compound, and 0.002 to 0.4 millimole of selected metal per gallon of said gasoline, of a gasolinesoluble salt selected from the group consisting of alkali metal and alkaline earth metal salts of a phosphorus compound having the formula:

wherein R is a hydrocarbon radical of up to 30 carbon atoms on the average, R is selected from the group consisting of hydrogen and R and S is sulfur. The gasoline composition may additionally contain about 0.05 to 0.6 theory of a gasoline' soluble phosphorus compound having the formula:

wherein R is a hydrocarbon radical of up to about 30 carbon atoms on the average, R is selected from the group consisting of hydrogen and R, and n is an integer having a value of 0 to 1.

Ser. No. 796,277, filed Dec. 16, 1964 is a continuation of Ser. No. 418,855, filed Dec. 16, 1964 and now abandoned.

The present invention relates to distillate hydrocarbon gasoline compositions which when employed in spark ignition engines lead to improved engine performance.

One of the chief disadvantages attending the use of known additives to lessen abnormal combustion of gasoline in, for instance, automobile engines is that they adversely affect the nature and increase the amount of deposits in the combustion space. These effects manifest themselves in a variety of ways particularly in the case of the higher compression engines. For instance, a fuel having an octane number appropriate to the designed engine compression ratio is unable to give the same antiknock performance after the formation of extensive deposits. To obtain the intended anti-knock performance requires a fuel of higher octane number, and this effect has become known as the octane requirement increase or ORI of the engine. Modern engines also evidence a tendency to rumble, an objectionable shuddering noise, apparently caused by flexing of the crankshaft due to deposit-induced abnormal combustion. Surface ignition induced by deposits also often creates abnormalities such as pre-ignition, auto-ignition and wild ping. Combustion chamber deposits are known to cause piston ring wear and to reduce exhaust valve life. All of these facets of combustion abnormalities can lead to engine damage and/ or loss in power and elficiency.

Various commonly employed gasoline additives as, for example, phosphate compounds such as tricresyl phoslice phate, cresyl diphenyl phosphate, etc., are known to improve engine operation with respect to certain of the problems presented by deposit-induced ignition. Relatively large amounts of these compounds are needed, however, to effectively combat the combustion abnormalities, particularly rumble.

It has now been found that leaded gasolines having added thereto about 0.002 to 0.4 millimole of metal per gallon of gasoline-soluble alkali or alkaline earth metal salts of certain phosphorus compounds, exhibit improved engine performance with respect to one or more of lower octane number requirement increase, improved rumble, surface ignition characteristics, reduced piston ring wear and extended exhaust valve life. The preferred alkali metal salts are those of sodium, potassium and lithium and the preferred alkaline earth metal salts are those of calcium and barium.

The phosphorus compounds, the alkali and alkaline earth metal salts of which constitute the additives of the invention are dithiophosphoric acid esters having the following formula:

RO SE i RO s wherein R is a hydrocarbon radical of up to about 30 or more carbon atoms on the average, often at least about 5 and preferably about 8 to 18 carbon atoms, R is hydrogen or R, and S is sulfur. R can be an aliphatic, aromatic or mixed aliphatic-aromatic radical and is preferably non-olefinic and non-acetylenic, i.e., having adjacent carbon atoms no closer than 1.40 A. The total number of carbon atoms in a molecule of the phosphorus compound is preferably up to about 40 or even up to about 30 and the alkaline metal salt of the phosphorus compound is soluble in gasoline at least to the extent employed in this invention.

The phosphorus compounds from which the metal salts of the invention are made can be obtained by methods known to the art as, for instance, by reacting aliphatic alcohols, including cycloaliphatic alcohols, or aromatic hydroxy compounds with P S The preferred alcohols are alkanols which can be straight or branch chained and alkyl-substituted phenols whose alkyl substituents contain a total of up to 18 carbon atoms, and preferably are lower alkyl, especially methyl. The aromatic hydroxy compounds and aliphatic alcohols may be substituted with non-deleterious groups. Illustrative of suitable alcohols are pentanol, butanol, octanol, isooctanol, Z-ethyl-heptanol, dodecanol, oleyl alcohol, octadecyl alcohol, tetradecyl alcohol, alcohols prepared by the 0x0 process, phenol and alkylated phenols such as cresol, xylenol, propyl phenol, butyl phenol, dibutyl phenol, monoamylphenol, diamyl phenol, decyl phenol, dodecyl phenol, tetradecyl phenol, hexadecyl phenol and octadecyl phenol.

The reaction of the alcohol and P 8 to prepare the partial esters or thioesters can be conducted by heating the reactants at temperatures of from about C. to about C. for a period of time sufiicient to effect substantially complete reaction, usually about 1 to 15 hours. An inert solvent such as toluene, xylene or the like may be used to facilitate the reaction. A suitable molar ratio of alcohol to P S may be about 3: 1.

The ester products thus produced can be, for instance, monoalkyl, dialkyl, monoaryl or diaryl esters of dithiophosphoric acid, or any combination thereof. The mixed esters are often present, for instance, in a mole ratio of at least about 25% of each, say about 60 to 40% monoester: 40 to 60% diester. The metal salts of the esters can be prepared by directly reacting the esters with an alkali or alkaline earth metal carbonate or acetate. Either the metal or the acidic component of the salts may be used in excess and either the monoor di-partial ester salts may be employed but they are conveniently prepared and made available as the mixed ester salts. Mixed alkali and alkaline earth metal dithiophosphates may also be used.

In order to provide leaded gasolines of further enhanced characteristics, for instance, as to preignition, spark plug fouling and even, in at least some cases, rumble, there can be included in the gasoline composition of the invention a gasoline-soluble phosphorus compound having the formula:

B On

wherein R has the value described above with respect to the phosphorus compounds from which the cobalt and nickel salts of the invention are made; R is hydrogen or R and n is an integer of to 1. R is preferably an aromatic, e.g. phenyl, hydrocarbon radical of 6 to 12 carbon atoms and can be substituted as, for instance, with lower alkyl groups say of 1 to 4 carbon atoms. Thus, the phosphorus compound can be a mono-, di-, or triester, or a mixture of such and is preferably a triester. We also prefer to employ a phenyl, alkyl phenyl or a mixed phenyl-alkyl phenyl ester of phosphorus. Thus, one or more of the ester groups is preferably an alkyl phenyl radical, often of about 7 to 15 carbon atoms. See US. Patent No. 2,889,212 for a further list of the useful phosphates and phosphites.

These auxiliary phosphate and phosphite additives can be prepared by reacting the appropriate alcohol or phenol with phosphoric acid to make the phosphate or with phosphorus trichloride to form the phosphite. Illustrative of suitable alcohols and phenols are those mentioned above in the description of the phosphorus esters used to form the metal salts of the invention. Examples of suitable alkyl phenols are ortho, meta and para cresol, 2,4- and 2,5-xylenol; 2,4-dimethyl-6-tertiary butylphenol; octyl and nonyl phenols, etc.

By the term leaded gasoline to which the additives of the present invention are incorporated is meant hydrocarbon fractions boiling primarily in the gasoline range, usually about 100 to 425 F., having added thereto a small amount, generally between about 1 to 6 cc. per gallon, preferably about 2 to 4 cc. per gallon, of a tetralower-alkyl lead compound as an anti-knock agent. The gasolines are usually composed of a major amount of a blend of hydrocarbon mineral oil fractions boiling primarily in the aforementioned range and will contain varying proportions of paraffins, olefins, naphthenes and aromatics derived by distillation, cracking and other refining and chemical conversion processes practiced upon crude oil fractions. Straight run gasolines, gasolines derived from cracking gas oil, gasolines or reformate from reforming straight run naphtha over a platinum-alumina catalyst in the presence of hydrogen, etc., are components frequently used in making up a gasoline composition. A typical premium gasoline, besides containing a small amount of a tetra-lower-alkyl lead compound as an anti-knock agent may also contain small amounts of other non-hydrocarbon constituents used to impart various properties to the gasoline in its use in internal combustion engines, e.g. halohydrocarbon scavengers, oxidation in hibitors, etc. Such gasolines frequently have a Research Method octane number of about 90 to 105, and a Motor Method octane number of about 80 to 98.

The metal thiophosphate salt component of the invention is incorporated in the leaded gasoilne in small amounts sufficient to provide a composition exhibiting an advantage in spark-ignition engines with respect to one or more of reduced surface ignition tendenecies, improved numble characteristics, lower octane number requirement increase, reduced ring wear and longer exhaust valve life. The actual amount of the metal salt additive employed may vary depending upon the particular gasoline used, its lead content, etc. In any event sufficient of the metal salt is employed to supply 0.002 to 0.4, preferably 0.025 to 0.3 millimole of the metal per gallon of gasoline. The additive will usually provide the gasoline with 0.00004 to 0.008 gram of alkali or alkaline earth metal per gram of lead, preferably 0.0005 to 0.006 gram of calcium or barium per gram of lead. This often means that about 0.5 to 15 or 20 or more pounds of the metal salt ester is added, preferably about 4 to 10 pounds, per 1000 barrels of gasoline. When used, about 0.05 to 0.6 theory, preferably about 0.15 to 0.5 theory, of the auxiliary phosphate or phosphite additive, based on the lead content of the gasoline, is generally employed. The term theory as applied to the amount of the second phosphorus additive means the amount required to react stoichiometrically with the lead so that all of the lead atoms and all of the phosphorus atoms form Pb (PO The following example is given to illustrate the advantages provided leaded gasolines by the additives of the present invention.

EXAMPLE I The sodium salt of hexyldithiophosphoric acid ester is prepared as follows: Four moles of hexanol were reacted with one mole of P 5 to form mixed monoand dihexyldithiophosphoric acid ester. A slight excess over one mole of sodium carbonate was reacted with each mole of the ester to form the sodium salt. The reactions were carried out at C. with the resulting product being filtered, water-washed, hydrocarbon-washed (benzene), then dried at 80 C. to constant weight.

The sodium salt thus prepared is added to a base gasoline in an amount of about 8 pounds/ 1000 barrels of gasoline and the composition was evaluated regarding its surface ignition characteristics. The base gasoline consisted of 14% straight run gasoline, 33% light catalytically cracked gasoline, 46% heavy catalytically reformed gasoline and 7% butane. Also included in the base gasoline were 3.0 cc. of tetraethyllead admixed with an ethylene dichloride scavenger and 0.2 theory diphenyl cresyl phosphate.

Evaluation of the resulting composition in a spark ignition engine shows operation of engine to be improved with respect to rumble, surface ignition characteristics, lower octane number requirement increase, reduced ring Wear and longer exhaust valve life.

EXAMPLE II Results similar to those of Example I can be obtained by adding to the leaded gasoline of Example I 108 pounds per 1000 barrels of the calcium salt of hexyldithiophosphoric acid ester prepared according to the procedure described in Example I.

The ORI of an engine is obtained by the following procedure:

After determining the clean or initial octane requirement of a 327 cubic inch 10.0:1 compression ratio engine, the gasoline without the additive of the invention is run for 216 hours and the octane requirement increase noted. The engine is then thoroughly cleaned of all deposits so that it again exhibits the same clean octane requirement increase and run on an identical cycle, with the same gasoline but containing the additive of the invention. After 216 hours use, the octane requirement increase is noted and compared with the octane requirement increase found with the gasoline without the additive to determine the extent of improvement.

The rumble tendency of an engine after a given time of use is measured by a LIB number. The number repre sents the percent isooctane (containing 3 cc. TEL/ gallon) required in a blend with benzene (containing 3 cc. TEL/ gallon) after a given period of engine operation using the fuel under test, to avoid rumble at a given r.p.m., e.g.

2,000 r.p.m. The test procedure comprises stopping the gasoline to the engine at any given period of engine operation and employing as a fuel to the engine a fuel containing a certain percent of isooctane in an isooctane-benzene blend (containing 3 cc. TEL/gallon), manually opening the throttle at a given rate and recording the rpm. at which rumble occurs, if any in fact occurs. The faster you are able to run the engine with the lowest percent of isooctane in the blend the better the rumble resistance of the engine. Thus, the lower the LIB number the better the rumble characteristics of the engine. The gasoline with and without the additive of the invention is tested in this manner and the LIB number obtained by each is compared.

The piston ring wear is determined by equipping a single cylinder COT engine with radioactive rings installed in the grooves of the pistons. The lubricating oil system of the engine is provided with a sealed monitoring well which contains a scintillation counter. The ring wear rate is determined by passing the lubricating oil through the monitoring well and therein detecting the concentration in mg./hour of radioactive iron transported to the oil due to wear of the piston rings.

The test to determine the effect of the fuel composition on exhaust valve life involves running an automobile engine at a fixed number of hours at constant or varied speeds and loads depending on the engine used and then noting the number of valves that failed during this period of time.

The test used to determine the deposit-induced ignition characteristics of the fuel composition comprises equipping an engine with an L-head cylinder and an electronic wild ping counter which records the total number of wild pings which have occurred during the test periods. Since deposit-induced ignition is the tendency to ignite the fuel-air mixture erratically and to produce uncontrolled combustion noticeable as, for instance, wild ping, the electronic counter which is used in conjunction with an ionization gap, automatically detects and records uncontrolled combustion.

It is claimed:

1. A gasoline composition consisting essentially of hydrocarbon gasoline, an anti-knock quantity of tetra-loweralkyl lead compound, and 0.002 to 0.4 millirnole of selected metal per gallon of said gasoline, of a gasolinesoluble salt selected from the group consisting of alkali metal and alkaline earth metal salts of a phosphorus compound having the formula:

R0 SH R'O s wherein R is a hydrocarbon radical of up to 30 carbon atoms on the average, R is selected from the group consisting of hydrogen and R and S is sulfur.

2. The composition of claim 1 in which there is also included about 0.05 to 0.6 theory of a gasoline-soluble phosphorus compound having the formula:

wherein R is a hydrocarbon radical of up to about 30 carbon atoms on the average, R is selected from the group consisting of hydrogen and R, and n is an integer having a value of 0 to 1.

3. The composition of claim 2 wherein at least one R in the structure of claim 2 in an alkyl phenyl radical of 7 to 15 carbon atoms.

4. The composition of claim 3 wherein the amount of phosphorus compound is about 0.15 to 0.5 theory.

5. The composition of claim 1 wherein the metal is alkali metal.

6. The composition of claim 1 wherein the metal is alkaline earth metal.

7. A gasoline composition consisting esentially of hydrocarbon gasoline, an anti-knock quantity of a tetralower-alk yl-lead compound, and about 0.025 to 0.3 millirnole of selected metal per gallon of said gasoline, of a gasoline-soluble salt selected from the group consisting of alkali metal and alkaline earth metal salts of a phosphorus compound having the formula:

R0 SH wherein R is an alkyl radical of 8 to 18 carbon atoms on the average, -R' is selected from the group consisting of hydrogen and R and S is sulfur.

8. The composition of claim 7 in which there is also included about 0.05 to 0.6 theory of a gasoline-soluble phosphorus com-pound having the formula:

wherein R is a lower alkyl phenyl radical of 7 to 15 carbon atoms and R is selected from the group consisting of phenyl and R.

9. The composition of claim 8 wherein the metal is sodium.

10. The composition of claim 9 wherein the nonmetallic phosphorus compound is cresyl diphenyl phosphate.

References Cited UNITED STATES PATENTS 2,777,874 1/1957 Asseff et a1. 260429.7 2,889,212 6/1959 Yust et al. 4476 FOREIGN PATENTS 795,658 5/1958 Great Britain.

DANIEL E. WYMAN, Primary Examiner Y. H. SMITH, Assistant Examiner US. Cl. X.R. 4476 

